GPS: It Took A Long Time

Last week Garmin reminded us that it was 20 years ago that the GPS 155 was the first to receive FAA approval for IFR navigation en route, terminal and for approach. Even in the slow moving world of aviation technology 20 years is a long time. But the surprising saga of how GPS got to be what we know today goes back much further.

I’ve been following and writing about GPS for nearly 40 years. I started trying to describe the technology in 1975 when I was working in the communications department at Collins Radio, what we now know as Rockwell Collins. The then large conglomerate, Rockwell, had just acquired Collins and the sometimes bumpy road to integration was under way.

Collins engineers had been working on a previously secret satellite based navigation system for the Air Force called Navstar. Collins had the contract to build the first receivers and another division of Rockwell was building the satellites.

Navstar was first, foremost and at that time exclusively a weapons system. Or more precisely a weapons guidance system. It was the winning technology after years of research, trial and error to find a way to locate and direct military weapons, missiles, aircraft, ships and even individual soldiers anywhere on earth.

The Cold War was burning hot at the time and Navstar would give the U.S. a big edge in precision weapons delivery. Before Navstar inertial guidance was the best technology for directing weapons to their targets over long range, but inertial has many limitations, including accumulating errors as time and distance go by.

I don’t know for sure why the Air Force decided to begin talking about Navstar. Maybe the program became too big to keep secret. Or maybe it understood that once a signal is broadcast it can’t really be a secret. Or maybe it wanted some PR. Whatever the reason by 1975 we could start talking at least a little about Navstar and its fantastic capabilities. Navstar performance was still secret and we could only say accuracy was “within 10s of meters” and there were only a few test satellites overhead. But Buick signed up to be the first auto maker to eventually offer Navstar guidance. And Collins was able to show off the precision of Navstar guidance by flying its Sabreliner under the short and small reception footprint of the few test satellites.

The FAA reaction to Navstar was no, never, will the signals be used for civilian airplane navigation. Don’t even think about it. The Air Force reinforced the FAA by letting everybody know that it is intentionally degrading the accuracy of Navstar by “dithering” the signal and only military receivers with “selective availability” could receive the true nav accuracy. And on top of that the Air Force said it will turn off Navstar at any time it wants and without any warning or notice.

You can imagine how this played in the rest of the world. Even our allies were never ever going to use a nav system controlled by the U.S. military. The FAA and Europeans threw millions at the microwave landing system (MLS) while all the while swearing on a stack of whatever that we civilians would never be allowed to use Navstar guidance in the national airspace system.

But, once you put a signal out there, somebody is going to figure out how to receive it and use it. And people did. Before long people were creating Navstar receivers for all sorts of uses. None of those receivers were approved for anything, but they didn’t need to be, except in aviation for IFR navigation.

Soon the Navstar name was dropped in favor of the more descriptive Global Positioning System. The FAA and Air Force remained adamant that GPS couldn’t be used for any approved navigation. The Air Force kept telling the public it would degrade GPS accuracy and may turn it off at any time it saw a threat. But companies kept building ever more capable navigators and GPS began to work its way into all aspects of our lives.

By the Clinton administration the politicians realized the Air Force attitude was untenable. Taxpayers understood that they had paid for the GPS technology development and for the satellites and wanted to use what they had paid for. President Clinton was the first to order the Air Force to knock off all the GPS denial talk and remove the intentional error from the system.

The FAA did a complete 180 turn and announced plans to convert to a complete satellite based nav system. There would be no more ILS approaches and the VORs would be decommissioned on a schedule that was too rapid to be believable. WAAS solved the problem of insufficient vertical accuracy and signal loss warning time so LPV approaches match the precision of ILS. The FAA remains committed to a satellite based air space system but the timetable has slipped to 2020 and beyond.

And the rest of the world jumped onboard. The Europeans have the Galileo satellite system, the Russians have GLONASS, and China and others are developing their own more or less compatible GPS systems and all will eventually be integrated into worldwide system.

The surprise wasn’t that politics, both military and civilian, got in the way of all of us using GPS. The pleasant, and rare surprise, is that all of us won. Most new technology is launched with promises that can’t be kept. GPS was launched with promises that the world, and particularly civilian pilots, wouldn’t be able to use it. Funny how hard it is to predict where technology will lead.

11 Responses to GPS: It Took A Long Time

In the early 70′s, the aircraft parking ramp at Kadena Air Base Okinawa was being surveyed. Aircraft parking slots were being drawn with accuracy to a few feet. Word at the stag bar said that an aircraft (F-4 at the time) would be able to navigate from the parking spot, to a target, and return to the same parking spot using the new system.

In my 50+ year old Skyhawk, the only new stuff is the iPad and ADSB. Wiley Post and Amelia Earhart would recognize everything else with ease.

Hi Mac,
Your comments about GPS reminded me of my Navy experience with what was referred ton as “NAVSAT.” I was in the submarine service, worked in the navigation department aboard an FBM (fleet ballistic missile) submarine. We used SINS (ships inertial navigation system) for supplying fire control with position information, and secondarily, for navigation. At night, we would come up to periscope depth, raise the NAVSAT antenna. and get a position fix to correct for inherent drift in the SINS, as well as to monitor Loran-C position data. Today, we think nothing of GPS, often taking it’s capabilities for granted in our planes, cars, boats, or just hiking the backwoods. Back in the ’70s, it was a classified, and a “wonderful” technology. How times have changed, and isn’t it great to be alive today with the benefits of GPS! I Always enjoy reading “Left Seat.”

GPS want from being a Positioning and Targetting system to a Navigation system because Asst Sec Def Don Latham wrote a one page directive in May 89 that told the military to use GPS as a replacement for TACAN in the National Airspace I was lucky to work with CDR Bill Mugg and Bill Volkstadt who converted that into about a 10-15 page document on how to use GPS in the National Airspace. We didn’t ask the FAA, we told them how we were going to do it, and when DOD went down that path FAA couldn’t keep the others from following.

To be fair, I think Garmin has done okay with their boxes. My frustration is with the cost of the data. I’d like to see the FAA’s regular (taxpayer-funded) data releases be usable without paying Garmin a pound of flesh all the time. I give more to Garmin than I pay for maintaining the entire aircraft.

Hi Bob,
I guess your concern is the price, because several WAAS enabled GPS navigators with no com or VHF nav do exist and are fully qualified for LPV and other GPS procedures. There is a limit on how “simple” a full capability GPS can be because it must have a full database and its functions must be automated in terms of leg sequence and so on.
Mac Mc

Price is exactly the concern. The closest to this “basic” unit on the market–Garmin’s 400W–is apparently now discontinued in favor of “deluxe” models with extra features at twice the price or more, and the supply of used ones will slowly dwindle. $4k wouldn’t be too terribly bad a price for a new unit, though $50/month/unit data updates seem really steep when one can get full data packages (sectionals, charts, plates, AFD, etc) for $100/year from other vendors.

Maybe in a few years, when it’s time to build my panel, someone will have a competitor/successor unit for the 400W at a reasonable price, and which doesn’t duplicate the other functionality that already comes in any modern experimental EFIS. But then, maybe I’ll win the lottery, too.

Bob sez, “Garmin’s 400W–is apparently now discontinued in favor of “deluxe” models with extra features at twice the price or more, and the supply of used ones will slowly dwindle. $4k wouldn’t be too terribly bad a price for a new unit, though $50/month/unit data updates seem really steep when one can get full data packages (sectionals, charts, plates, AFD, etc) for $100/year from other vendors. ”

Exactly. I quit buying Garmin because of their ridiculous charges for updates. iPad and WingX solved the problem quite nicely.